The U.S. dollar was as low as 114.73 yen but recently was trading a full yen above that low, at 115.73 yen or about 0.5 percent off the previous U.S. close. The dollar was as high as 116.19 yen to start the trading day Thursday.

"It really is still a one-way street" of selling dollars for yen, said Peter Frank, analyst with ABN Amro Global FX Research. He expects more pressure on the dollar-yen rate.

Traders said Tokyo officials were less likely to intervene by buying dollars ahead of a weekend Group of Seven meeting in Dubai, at which Japan is expected to be scolded by its fellow industrial power leadership for aggressive intervention this year.

U.S. Treasury Secretary John Snow, at the urging of U.S. manufacturers, is expected to lead the effort to urge the Japanese to let market fundamentals determine the value of the yen.

A depressed yen keeps Japanese exports competitive on world markets, a key component of the world's second largest economy.

At the same time, it is believed the piercing of the 115-yen level might cause officials to reconsider their hands-off approach, prompting the dollar buying.

"It'll be awfully hard for the [Bank of Japan] to do anything now," said Frank.

The Bank of Japan and Japan's Ministry of Finance had no comment on Thursday when asked whether Japan had intervened in the currency markets, according to media reports.

Frank said that U.S. stock gains typically help the dollar but so far, U.S. gains only continue to lead Japan's Nikkei average to fresh 15-month peaks on bets for stronger Japanese growth, which continues to fuel demand for yen over dollars.

U.S. economic reports were essentially ignored. They showed a drop in the weekly number of jobless benefit requests and the fourth monthly gain for leading economic indicators, as well as a mixed reading on Philadelphia-area manufacturing growth. See more on jobless claims and leading economic indicators. Get the full story on the Philly Fed index.

The euro recently fell 0.2 percent against the dollar at $1.1250 but had traded in both directions in a choppy session. The euro fell 0.8 percent to 129.79 yen.

The dollar edged up 0.1 percent on the Swiss franc, at 1.3799 francs, after the Swiss National Bank on Thursday left key short-term rates unchanged, as expected.

The British pound rose 0.6 percent to $1.6175 as traders digest monetary policy meeting minutes issued earlier this week that showed some members growing more inclined to raise interest rates.

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